Recently, in order to meet a demand for high-speed field effect transistor, there is required a technique for forming a laminated structure in which a Si film and a SiGe film are alternately laminated and then performing selective side-etching of the Si film with respect to the SiGe film.
Patent Document 1 discloses therein a technique for performing plasma etching by using, as an etching gas, one or more gases containing carbon atoms, hydrogen atoms and fluorine atoms, e.g., a gaseous mixture of SF6 gas, H2 gas, CF4 gas and Ar gas, while setting a partial pressure of the fluorine atoms to 1.0 Pa or less.
Patent Document 1: Japanese Patent Application Publication No. 2013-251471
However, the technique of Patent Document 1 requires a complicated gas system and a gas needs to contain fluorine that is harmful. Further, since the partial pressure of the fluorine atoms needs to be 1.0 Pa or less, a range of a processing condition to obtain desired selectivity is obtained is narrow.